On Fri, 30 Oct 2015 19:04:07 -0000, Ian Field wrote:



"Tough Guy no. 1265" wrote in message
news
On Fri, 30 Oct 2015 18:48:26 -0000, Ian Field
wrote:



"Tough Guy no. 1265" wrote in message
news On Fri, 30 Oct 2015 17:10:19 -0000, Tough Guy no. 1265
wrote:

https://www.dropbox.com/s/fy5xm8lmd3....jpg?dl=0&s=sl

This supply came with a 2 foot 9W strip light of LEDs. After 1 week it
began flickering badly. 240V AC in on the right. The circuit outputs
75V DC on the left, with a 3.5V AC ripple on it (with the 100uF
capacitor
included, which I verified is ok). With a 680uF capacitor in its
place,
there is no visible flicker.

What's likely to have broken in this circuit?

What's the chances of it lasting if I run it with the larger capacitor?

Forgot to add, I checked the voltage and current output with the larger
capacitor, and it was virtually identical.

When you first switch on, the fully discharged capacitor looks like a
dead
short for the split second it takes to charge up. The bigger capacitor
will
cause the turn on surge to last nearly 7x longer.

The LEDs light up very slowly with the bigger capacitor (for half to one
second perhaps), so I think it's being limited. Also, when I turn it off,
won't the capacitor stay charged to the voltage just below what's required
to make the LEDs conduct, so it's not going to be empty at the next
startup?

If the circuit has a NTC thermistor inrush limiter, you're probably OK.
I usually look for them in any equipment I scrap, when I still used
filament
bulbs - one of those added behind the switch plate makes the bulb last
years.

They look similar to a disc ceramic capacitor about 10 - 15mm diameter,
they
tend to be dull green or black and have a matt finish as compared to
capacitors that are usually shiny finish.

I can't see one. There's a resistor connected directly to neutral on the
bottom right of the photo. In series with that resistor are the two
capacitors (blue and yellow), going across to live.

Post a photo.

The link is at the top of this post, you must have missed it.

--
What comes after 69?
Mouthwash.